You don't have to trust me, but here is the actual science and what doctors and researchers are saying about it:

New England Journal of Medicine:

Authorized mRNA vaccines were highly effective among working-age adults in preventing SARS-CoV-2 infection when administered in real-world conditions, and the vaccines attenuated the viral RNA load, risk of febrile symptoms, and duration of illness among those who had breakthrough infection despite vaccination.

.https://www.nejm.org/doi/full/10.1056/NEJMoa2107058?query=featured_home

CDC:

COVID-19 vaccines are effective at preventing infection, serious illness, and death. Most people who get COVID-19 are unvaccinated. However, since vaccines are not 100% effective at preventing infection, some people who are fully vaccinated will still get COVID-19. An infection of a fully vaccinated person is referred to as a “vaccine breakthrough infection.”

The COVID-19 vaccines authorized in the United States are highly effective at preventing severe disease and death, including against the Delta variant. But they are not 100% effective and some fully vaccinated people will become infected (called a breakthrough infection) and experience illness

.https://www.cdc.gov/coronavirus/2019-ncov/vaccines/effectiveness/why-measure-effectiveness/breakthrough-cases.html

John Hopkins Medicine:

An effective vaccine will protect someone who receives it by lowering the chance of getting COVID-19 if the person encounters the coronavirus. More important is whether the vaccine prevents serious illness, hospitalization and death. At this time, all three vaccines are highly efficacious at preventing serious illness, hospitalization and death from COVID-19.

.https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/covid-19-vaccine-what-you-need-to-know

Annals of Internal Medicine:

Currently used vaccines against SARS-CoV-2 infection are highly effective in preventing confirmed infection in a high-risk population in a real-world setting.

.https://www.acpjournals.org/doi/10.7326/M21-1577